Heating, ventilation and air-conditioning (“HVAC”) systems are used in all types of commercial, industrial and residential facilities (hereinafter referred to as “buildings”). In general, the HVAC system is designed to maintain various predetermined set points, such as temperature. To that end, a system that generates hot air may be controlled on or off depending on the need for heat in a particular location. The supply of conditioned air (hot or cold) may further be controlled by the use of dampers within the air supply system. In larger buildings, the dampers may be actively controlled to regulate the supply of conditioned air.
HVAC systems in larger buildings tend be located at a significant distance from the spaces that they are servicing, and a single HVAC unit may be used to provide conditioned air to several different floors. To this end, ducting is required between the various floors, a number of dampers are needed to regulate the distribution of air between the various levels, and additional insulation around the ducting is needed to reduce heat loss from the ducting. The result is reduced efficiency, additional material cost, and additional space requirements for a given HVAC system.
Moreover, conditioned air is generally provided by an HVAC system based upon a sensed out of limits condition. In other words, when the temperature in a room is determined to be too warm, cool air is supplied to the room so as to bring the room back within a controlled band. The HVAC systems are accordingly reactive to actual changes in temperature. While this is effective, it results in undesired variances in temperature. Moreover, as the magnitude of the change in temperature increases, the amount of energy required to drive the temperature back into the desired range in a given amount of time also increases. Thus, a larger HVAC system is needed to provide the needed capacity. As the size of the HVAC system increases, larger ducting is needed for the increased volume of air and more energy is required to power the HVAC system. The result is reduced efficiency, additional material cost, and additional space requirements for a given HVAC system.
Some of the above limitations result from the approach used to regulate, monitor and control the various machines as well as environmental and safety aspects of buildings. For example, to facilitate control over various aspects of a building, control systems employ sensing devices that measure various conditions, such as temperature, air flow, or motion. Other sensors determine the presence of smoke, the presence of dangerous or noxious chemicals, light and the like.
Typical sensor devices for such uses are expensive. Accordingly, the number of sensors used in a particular application is limited to the minimum number required in order to reduce costs. For example, in many residential systems a single temperature sensor is used. Similarly, the temperature within a conference room may be controlled based upon the sensing of a single instrument. Such limited sensing results in large temperature differentials throughout the space. Such temperature differentials result not only in reduced comfort for the individuals in the building, but also reduced efficiency in the HVAC system as discussed above.
The above illustration is indicative of a larger problem with prior art building control systems. Namely, prior art building control systems are designed to operate with very limited knowledge of the building that they are incorporated into. There is little understanding within the building control system of the activities within and around the building that affect the environment such as weather conditions, the operating status of machinery and equipment, or the number of people in the building.
Moreover, the building itself may provide a significant contribution to the internal environment. This is particularly evident in the instance of a building with a large amount of glass on a sunny day. In such instances, the glass may provide significantly to the heating of the building. Yet, prior art buildings contribute little to the active control over the internal environment. Thus, the building control system must be manually configured to avoid significant overheating of one side of a building while under heating areas that are not exposed to the sunlight.
As a consequence, there is a need for apparatus and method that can reduce at least some of the drawbacks and costs identified above. For example, there is a need for a method and/or apparatus that reduces the costs associated with the sensing devices that are necessary for sensing conditions within a building control system. There is a further need for a system that incorporates building components into the building control network so as to better control fluctuations in the building environment. There is yet a further need for a building control system that includes sensors located close to the source of heat and cold disturbances within a building so as to provide for more rapid moderation of the disturbances.